Adaptive sprinkler head

ABSTRACT

A sprinkler head for fixed fire extinguishing systems of the type in which a fluid extinguishant is supplied under line pressure to a plurality of such heads, in which the actuation of the head in response to fire is inhibited when line pressure drops below a predetermined magnitude, thereby to preserve the ability of already actuated heads in the system to disperse extinguishant on a fire. In one embodiment, a movable heat shield is employed together with line pressure responsive means for controlling the position of the heat shield with respect to the sprinkler head fuse. In another embodiment, a pressure responsive valve is employed to permit passage of extinguishant through a bleed conduit directly to the fuse thereby to effect cooling thereof.

United States Patent Livingston 1 ADAPTIVE SPRINKLER HEAD [72] Inventor: William L. Livingston, Sharon,

Mass.

[73] Assignee: Factory Mutual Research Corporation, Boston, Mass.

[63] Continuation of Ser. No. 885,501, Dec. 16

1969, abandoned.

[1 1 3,684,025 [451. Aug. 15, 1972 Tyden 169/37 Primary Examiner--Lloyd L. King Assistant Examiner-Thomas C. Culp, Jr. Attorney-Lane, Aitken, Dunner & Ziems [57] ABSTRACT A sprinkler head for fixed fire extinguishing systems of the type in which a fluid extinguishant is supplied under line pressure to a plurality of such heads, in which the actuation of the head in response to tire is inhibited when line pressure drops below a predetermined magnitude, thereby to preserve the ability of already actuated heads in the system to disperse extinguishant on a fire. In one embodiment, a movable heat shield is employed together with line pressure responsive means for controlling the position of the heat shield with respect to the sprinkler head fuse. In another embodiment, a pressure responsive valve is employed to permit passage of extinguishant through a bleed conduit directly to the fuse thereby to effect cooling thereof.

18 Claims, 6 Drawing Figures [52] U.S.Cl. ..l69/37, 169/42 [51] lnt.Cl. ..A62c 37/08 [58] Field of Search ..169/37, 38, 42; 239/487 [56] References Cited UNITED STATES PATENTS 3,590,924 7/1971 Emmons eta]. ..l69/17 3,454,097 7/1969 Groos ..l69/38 3,388,747 6/1968 Hodnett ..169/42X 3,314,482 4/1967 Young ..169/37X iiim 1 10 x r 1 i l k 4/ ADAPTIVE SPRINKLER HEAD CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of Ser. No. 885,501, filed Dec. 16, 1969, now abandoned. This application is also related to an application entitled Fire- Responsive Sprinkler Head, Ser. No. 864,756, filed Oct. 8, 1969 (executed Oct. 3, -l969) by William L. Livingston and Sebastian David Tine.

BACKGROUND OF THE INVENTION This invention relates to sprinkler heads for fixed fire extinguishing systems of the type in which a fluid extinguishant is supplied under pressure to a plurality of such heads, each being operable independently to disperse extinguishant to an assigned area of coverage in response to fire conditions. More particularly, the invention is concerned with the provision of means in such sprinkler beads by which optimum performance of one or more heads actuated to extinguish a fire in their respective areas of coverage is in no way curtailed by the unnecessary opening of remote sprinkler heads and resulting loss of line pressure.

In fixed fire extinguishing systems of the type with which the sprinkler head of the present invention is intended to be used, it is conventional practice to locate a plurality of the heads at predetermined spacing near the ceiling of the building space to be protected. Each of the heads is equipped with a fire sensing means, usually a thermally fusible element which opens or activates the head when a predetermined temperature in the vicinity of the fusible element is reached. The heads are in direct fluid communication with a source of extinguishant, such as water tapped from a municipal water main, by way of a plumbing system including risers, submains, branch lines and the like. Hence, as

will be apparent to one having only a modest familiarity with the principles of fluid flow, the amount of extinguishant available to a sprinkler head actuated in response to a fire in an existing system with given pipe size, will depend almost entirely on the line pressure under which extinguishant is supplied to the inlet of that particular head. Moreover, it is equally apparent that for a given amount of pressure in the municipal main or other source of extinguishant supply to the system, the extinguishant pressure at each head is diminished by the opening of each additional head in the system.

It is also imperative in fixed fire extinguishing systems of the type here involved that the fire responsive means associated with the respective heads be equally sensitive since it cannot be predicted where in the space protected, a fire is likely to occur and correspondingly, which of the heads is likely to be activated first in response to such a fire. Hence, where the fire responsive means is a thermally fusible element associated with each head, obviously each of the thermal fuses must be selected to respond to the same temperature. While this factor in and of itself would not appear to be a deterrent to satisfactory system operation, provided the amount of extinguishant initially dispersed by the first sprinkler heads in the system to be actuated is sufficient to actually extinguish the fire, it contributes to a serious deficiency with larger type fires which develop enough heat to activate remotely located heads which are incapable of delivering extinguishant directly to the fire. Specifically,'the actuation of such remote heads brings about a reduction in the line pressure supplying the sprinkler heads delivering extinguishant directly to burning fuel surfaces of the fire, a condition diametrically opposed to the basic purpose of the system. As a result, most fire extinguishing systems in existence at the present time provide adequate protection only for small fires of the type which are inconsequential from the standpoint of destroying a total building, and virtually ineffective against large fires which result in serious losses of property.

. SUMMARY OF THE PRESENT INVENTION In accordance with the present invention, many of the deficiencies in fixed fire extinguishing systems of the type heretofore available are avoided by preventing the actuation of sprinkler heads located remotely from those heads which are activated to deliver extinguishant directly to a fire, thereby insuring that the pressure of extinguishant at the activated heads is maintained. This mode of operation is accomplished by providing each head with a line pressure responsive means for inhibiting or delaying the fire responsive release device associated with the head when the pressure of extinguishant at that head is below a predetermined amount as a result of the opening of other heads in the system. structurally, the invention may take different forms, one embodiment involving a heat shield normally positioned by line pressure away from the usual thermally actuated fuse link for actuating the head. When line pressure drops as a result of other heads in the system being open, the shield is moved to a position about the thermal fuse so as to require a higher will proceed in a normal manner because the initial static pressure head of the system will be maintained above the pressure at which the delay mechanism associated with each head is brought into operation.

Among the objects of the present invention are therefore: the provision of a fixed fire extinguishing system in which optimum delivery of extinguishant to one or more sprinkler heads actuated in response to a fire is not in any way curtailed by the unnecessary opening of other sprinkler heads in the system positioned remotely from the fire; the provision of a sprinkler head for systems of the type referred to which is independently actuatable in response to the combined effects of temperature and pressure existing at the head when employed with a system incorporating a plurality of such heads; the provision of a sprinkler head of the type referred which is uncomplicated in its design and hence low in cost; and the provision of a pressure responsive delay mechanism for fixed fire extinguishing system sprinkler heads which is adaptable to existing system.

3 Other objects and further scope of applicability of the present invention will become apparent from the detailed description to follow and taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view depicting the operation of a fixed fire extinguishing system employing one form of the sprinkler heads of the present invention;

FIG. 2 is an enlarged cross-section of one embodiment of the present invention;

FIG. 3 is a side elevation in partial cross-section illustrating another embodiment of the present invention;

FIG. 4 is an enlarged fragmentary cross-section taken on line 4-4 of FIG. 3;

FIG. 5 is an enlarged cross-section taken on line 5-5 of FIG. 3; and

FIG. 6 is a fragmentary cross-section on a reduced scale taken on line 6-6 of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 of the drawings, a fixed fire extinguishing system is shown to include a plurality of sprinkler heads or noules 10a, 10b, 10c, 10d, 10c and 10f positioned in selected spaced relation about the ceiling 12 of an enclosed space 14 protected by the system. In conventional fashion, the nozzles 10 are supplied with a fluid extinguishant such as water from a municipal mater main (not shown) through a riser 16, a submain l8 and branch lines 20. The system is maintained with an extinguishant under pressure designated by the arrow P, the precise magnitude of which may vary depending on the system as well as the pressure available at the source of supply for the extinguishant. Each of the heads 10 is maintained in a closed position by a releasable plug or the like under the control of a fire responsive element 22, various embodiments of which will be described in more detail below.

For purposes of illustration, the space 14 shown in FIG. 1 contains combustible material or fuel piles designated by the reference letters F. The conventional operation of such systems, also depicted in FIG. 1 of the drawings, is such that when a fire exists within the space, the heat rising therefrom will be sensed by the fire sensing means associated with the head or heads 10 immediately above the fire to bring about actuation of the system. Hence, as shown, the development of a fire in the fuel piles beneath the head 10b will actuate that head to disperse extinguishant downwardly toward the fire. Also the heat developed by the fire is likely to bring about the actuation of immediately adjacent heads such as the heads 10a and 10b in FIG. I. Depending upon the magnitude of the fire and particularly of the heat generated thereby, a certain amount of time will elapse between the start of the fire and the actuation of the heads 10a, 10b and 100 to bring about its extinguishment. With smaller fires, it is possible that this time adequate the activation of a few heads to deliver a sufficient of extinguishant to extinguish the fire, thereby accomplishing the purpose for which the extinguishing system was installed. With larger fires however, where an extreme amounts of heat are developed, it often occurs that the circulation of heat by convection within the space 14 as depicted by the arrows H in FIG. 1, will bring about the actuation of heads positioned remotely from the actual fire, such as for example the heads 10d, 10c and 10f. Quite obviously, the actuation of such remote heads will have little or no effect upon the extinguishment of the original fire and moreover, will reduce the pressure available for those heads initially actuated and in operation dispersing extinguishant toward the fire in such a manner that the overall system is rendered ineffective to extinguish the fire.

One embodiment of a sprinkler head design in accordance with the invention by which the phenomenon described above with respect to FIG. 1 is overcome, is illustrated in FIG. .2 of the drawings. In this instance, the basic sprinkler head design is of the type disclosed in the above-mentioned copending application Ser. No. 864,756 filed Oct. 8, 1969 and includes essentially a body 24 having an inlet 26 adapted to be directly connected to one of the branch lines 20. An outlet orifice 28 is provided at the lower end of the body 24 and is normally closed by an expellable plug 30 secured at the lower end of a rod 32 retained by a transversely slidable pin 34 against displacement from the discharge orifice 28 under the influence of line pressure. As disclosed more fully in the aforementioned copending application, the nozzle head further includes swirling vanes 36 and a pressure responsive bellows 38 for varying the size of the discharge orifice 28 in accordance with line pressure. The retaining pin 34 is held against the bias of a compression spring acting on a collar 42 secured on the pin by a collapsible linkage assembly including arms 44 secured against collapse by a fusible link 46, this assembly in itself being well known in the fire extinguishing sprinkler head art. Hence, when temperature in the vicinity of the fusible link 46 reaches a predetermined point, the linkage including the legs 44 collapse out of the way, permitting the spring 40 to move the pin 34 out of engagement with the rod 32 to open the discharge orifice 0f the head 28.

In accordance with the present invention, the temperature at which the thermal fuse 46 is released, may be made dependent on line pressure at the associated sprinkler head 10 by means of a heat shield 48 positionable in response to fluid pressure within the body 24. To this end, the heat shield 48 is supported from a bell crank 50 pivoted from a tab 52 extending from a housing part 54 enclosing the pin 34 and fixed to the body 24. The depending arm 56 of the bell crank is formed with a slot 58 to receive a connecting pin 60 carried on the terminal end of a reciprocable plunger 62. The opposite end of the plunger 62 extends within a chamber 64 defined by a cap 65 threaded in a boss 66 on the body 24 and is connected to a flexible diaphragm 68. A port 70 in the boss 66 places the chamber 64 in fluid communication with the interior of the body 24 and thus with line pressure existing at the inlet 26 to the nozzle 10. A compression spring 72 acting between the cap 65 and a collar 74 on the plunger 62 biases the plunger and thus the bell crank 50 and heat shield 48 to the solid line position shown in FIG. 2 of the drawings. Line pressure, on the other hand, in the chamber 64 and acting against the diaphragm 68 tends to urge the plunger in a direction opposing the bias of spring 72 or to the phantom line position indicated in FIG. 2 of the drawings.

Thus, it will be seen that when line pressure existing within the body 24 is sufficient to overcome the biasing effect of the spring 72, the heat shield will be held in the position illustrated in phantom lines in FIG. 2 or away from the fusible element 46 which operates to effect actuation of the head in response to fire temperatures. When however, line pressure drops below a point at which the force exerted by the spring is larger than that developed by fluid pressure acting against the diaphragm 68, the heat shield 48 moves to a position about the fuse link 46 as shown.

The operation of the heat shield 48 in the system shown or depicted in FIG. 1 of the drawings will now be apparent. Initially, the line pressure P throughout the riser 16, submain 18, branch lines and the heads 10, being static, may be maintained at a point where the heat shield 48 associated with each head is maintained out of heat shielding position with respect to the respective fuse links 46. In this condition, and should a fire develop, each of the heads in the system is equally responsive to the temperatures resulting from the fire. Upon the development of a fire, those heads positioned directly thereover will be first actuated to disperse the extinguishant downwardly onto the burning fuel surface. If however, the line pressure drops below an amount determined by the biasing force of the respective spring 72, and where the possibility exists of inadequate extinguishant being directed toward the fire by heads already actuated or opened, the heat shields 48 for the remainder of the heads will move into the solid line position shown in FIG. 2 so as to delay or in hibit actuation of heads positioned remotely from the fire.

The heat shield 48 as shown in FIG. 2 is in the form merely of a metal trough like structure capable of absorbing or retaining heat as a'result of increased ambient temperatures so as to deter the effect of those temperatures on the fusible elements 46. It is possible however that other types of heat shields might be employed. For example, in some systems it may be desirable to provide the structure shown in FIGS. 2 with a liquid or gel coolant so that when the shield is moved to the solid line position shown in FIG. 2 the fusible element is actually immersed in the coolant. Some modification of the shape of the shield might be required where coolant is used in order to retain the coolant regardless of the position in which the shield unit may be disposed.

The alternative embodiment of the invention illustrated in FIGS. 3-6 of the drawings is particularly well suited for an application to existing systems using standard sprinkler head designs. As shown in FIG. 3, a branch line 76 is provided with a stand pipe portion 78 for supporting a sprinkler head 80, these components constituting but a portion of an extinguishing system including a plurality of branch lines or pipes, each supporting a plurality of heads, and extending horizontally at a level below the ceiling of the space to be protected. The nozzle 80 is of a well known commercial variety, thus including a body 82 with a discharge port 84 normally blocked by a plug 86 retained in place by collapsible linkage including lever arms 88. A standard loop or yolk 90 extends from the body 82 and supports a deflector disc 92 at its upper end by which the desired spray pattern of extinguishant passing through the 6 discharge opening is developed. As in the previous embodiment, a soldered thermal fuse 94 retains the collapsible linkage and thus the plug 86 in its unactivated or dormant condition.

Although normally, the body 82. of the sprinkler head would be threaded directly into the stand pipe portion 78 on the branch line 76, an adaptor coupling 96 is employed in accordance with this embodiment of the present invention. As shown in FIG. 3, the adaptor 96 is provided with internal threads 98 at its upper end for receiving the sprinkler head body 82 and with external threads 100 at its lower end to be received in the stand pipe portion 78.

Threadably received in the side of the adaptor 96 is a pressure responsive valve assembly 102 including a tubular mounting part 104 opened at its inner end and adapted to receive in threaded fashion a valve and drip tube supporting member 106 carrying a concentrically disposed axial tube 108 finished to define a valve seat 110 at its inner end. Slidably receivedwithin the tube 108 is a valve member 112 including a serrated or longitudinally grooved stern 114, a valve plug 116 and a retainer 118. As shown in FIG. 4 of the drawings, the retainer 1 18 is slotted radially from its outer edge to insure fluid communication through the open inner end of the mount 104 into the chamber in which the tube. 108 is located. The diameter of the retainer 1 18 is such that it cooperates with an inwardly directed flange 120 on the mount 104 so as to prevent escape of the valve member 112 through the inner end of the mount. A compression spring 122 positioned about the tube 108 exerts a slight bias tending to unseat the valve plug 1 16 from the seat 1 10 on the tube 108 thereby to enable the passage of fluid through the inner end of the mounting part 104, around the valve plug 116 and into the tube 108 along serrated valve stem 114. A bleed conduit in the form of capillary tube 124 of malleable metal, such as copper or the like, is suitably affixed in a boss 126 on the member 106 so as to be in fluid communication with the interior of the tube 108. The terminal end 128 of the capillary tube is positioned by appropriate bending to discharge line fluid against the thermal fuse 94 constituting the sprinkler head release mechanism.

In operation of the embodiment of FIGS. 36, under normal pressures existing in the line 76 and thus throughout the interior of the adaptor 96, the bias of the spring 122 will be overcome and the valve plug 1 16 will seat firmly against the seat 110 on the end of the tube 108, thereby to prevent passage of fluid into the capillary tube 124. In the event line pressure drops below the pressure at which the spring 122 is able to move the plug 116 away from seat 110 of the tube 108, line fluid will pass through the capillary tube 124 and be directed against the sprinkler head fuse 94 to effect a cooling thereof. Such cooling will, of course, delay actuation of the fuse or elevate the ambient temperature at which it releases to open the sprinkler head 80 in substantially the same manner explained above with respect to the heat shield 46 in the embodiments of FIGS. 1 and 2.

Thus it will be seen that by this invention there is provided an extremely effective means by which the sprinkler heads in a fixed fire extinguishing system may be made responsive to line pressure adequate for supplying extinguishant to heads which have been initially actuated and are in a position to direct an extinguishant to the burning fuel surfaces of a fire. While two embodiments of the invention have been disclosed, it will be appreciated by those skilled in the art that other modifications and/or variations of those embodiments disclosed can be made without departure from the present invention. Accordingly, it is intended that the foregoing description is illustrative of perferred embodiments only, not limiting, and that the true spirit and scope of the present invention be determined by reference to the appended claims.

1 claim:

1. [n a extinguishant dispersing head for fixed fire extinguishing systems of the type in which a fluid extinguishant is supplied under line pressure to a plurality of such heads, the combination comprising: means defining an inlet adapted to be placed in direct fluid communication with line pressure and an outlet for dispersing extinguishant, releasable means normally blocking fluid passage between said inlet and said outlet, fire sensing means operable upon the existence of a fire to release said means normally blocking fluid passage between said inlet and said outlet, and means responsive to line pressure at said inlet to inhibit operation of said sensing means when line pressure at said inlet falls below a predetermined magnitude.

2. The apparatus recited in claim 1 wherein said fire sensing means comprises a thermal fuse to release said blocking means at predetermined ambient temperatures.

3. The apparatus recited in claim 2 in which said means responsive to line pressure comprises a heat shield movable between a first position in which said fuse is exposed fully to ambient temperatures, and a second position in which said fuse is shielded thereby from increases in ambient temperature, and means to move said shield from said first position to said second position when pressure at said inlet drops below said predetermined magnitude.

4. The apparatus recited in claim 3 in which said means to move said shield comprises a flexible diaphragm, spring means biasing said diaphragm in a direction to move said heat shield to said second position and means communicating one side of said diaphragm with said inlet pressure to oppose a bias of said spring means and retain said shield in said first position as a consequence of said inlet pressure.

5. The apparatus recited in claim 2 wherein said means responsive to line pressure comprises a fluid conduit to direct line fluid against said fuse, and valve means to prevent passage of fluid through said conduit when pressure at said inlet is above said predetermined magnitude, said valve means being movable when pressure at said inlet falls below said predetermined magnitude to pass line fluid through said conduit and against said fuse.

6. The apparatus recited in claim 5 in which said conduit is formed of malleable material to enable adjustable positioning of the outlet end thereof.

7. The apparatus recited in claim 5 wherein said inlet defining means includes a tubular adaptor, said conduit and said valve means being mounted on said adaptor.

8. Apparatus for controlling the release temperature of a thermal fuse on a sprinkler head for fixed fire extinguishing systems of the type in which a fluid extinguishant under pressure is supplied by pipes to a plurality of such heads, said device comprising: actuating means movable from a first position to a second position in response to line pressure at the sprinkler head falling below a predetermined magnitude and means operably associated with said actuating means for inhibiting the effect of ambient temperature on said fuse upon movement of said actuating means to said second position.

9. The apparatus recited in claim 8 wherein said last mentioned means includes a heat shield movable to a position to shield said fuse from increases in ambient temperature upon movement of said actuating means to said second position.

10. The apparatus recited in claim 8 wherein said last mentioned means comprises a bleed conduit for directing extinguishant against said fuse, and wherein said actuating means comprises a pressure responsive valve which opens said bleed conduit upon movement of said valve from said first position to said second position.

11. The apparatus recited in claim 10 including a tubular adaptor for connection between the sprinkler head and the pipes of the fire extinguishing system, said bleed conduit and said valve being mounted in said adaptor, and said bleed conduit being deformable to adjust the discharge end thereof with respect to the fuse.

12. A fire protection system comprising at least one extinguishant discharge head mounted in an elevated position in the space to beprotected, means for supplying an extinguishant under line pressure to said head, releasable means normally preventing the discharge of extinguishant from said head, fire sensing means operable upon the existence of a fire to release said releasable means, and means responsive to a predetermined condition of said system to inhibit operation of said sensing means.

13. The system recited in claim 12 wherein said fire sensing means comprises a thermal fuse to release said releasable means at predetermined ambient temperatures. 7

14. The system recited in claim 13 in which said means to inhibit operation of said sensing means comprises a heat shield movable between a first position in which said fuse is exposed fully to ambient temperatures, and a second position in which said fuse is shielded thereby from increases in ambient temperature, and means to move said shield from said first position to said second position in response to said predetermined condition of said system.

15. The system recited in claim 14 in which said means to move said shield comprises a flexible diaphragm, spring means biasing said diaphragm in a direction to move said heat shield to said second position, and means communicating one side of said diaphragm with said extinguishant to oppose the bias of said spring means and retain said shield in said first position as a consequence of said inlet pressure.

16. The system recited in claim 13 wherein said predetermined condition of said system is a predetermined extinguishant pressure at said head and wherein said means to inhibit operation of said sensing means comprises a fluid conduit to direct line fluid against said fuse, and valve means to prevent passage of fluid through said conduit when the extinguishant pressure at said head is above said predetermined magnitude, ble positioning of the outlet end thereof.

sald Valve F b61118 l h Said P 18. The system of claim 12 wherein said predeterg i f ifigg i g gzitgfiq figg gfiggg g lme mined condition of said system is the extinguishant 17. The system recited in claim 16 in which said con- 5 pressure at each of said heads duit is formed of malleable material to enable adjusta- Disclaimer 3,684,025.T ViZZiam L. Livingston, Sharon, Mass. ADAPTIVE SPRINKLER HEAD. Patent dated Aug. 15, 1972. Disclaimer filed April 10, 1972, by the assignee, Factwy Mwtual Research Corporation.

Hereby disclaims the portion of the term of the patent subsequent to April 4, 1989.

[Ofiioial Gazette Januam 16, 1.973.] 

1. In a extinguishant dispersing head for fixed fire extinguishing systems of the type in which a fluid extinguishant is supplied under line pressure to a plurality of such heads, the combination comprising: means defining an inlet adapted to be placed in direct fluid communication with line pressure and an outlet for dispersing extinguishant, releasable means normally blocking fluid passage between said inlet and said outlet, fire sensing means operable upon the existence of a fire to release said means normally blocking fluid passage between said inlet and said outlet, and means responsive to line pressure at said inlet to inhibit operation of said sensing means when line pressure at said inlet falls below a predetermined magnitude.
 2. The apparatus recited in claim 1 wherein said fire sensing means comprises a thermal fuse to release said blocking means at predetermined ambient temperatures.
 3. The apparatus recited in claim 2 in which said means responsive to line pressure comprises a heat shield movable between a first position in which said fuse is exposed fully to ambient temperatures, and a second position in which said fuse is shielded thereby from increases in ambient temperature, and means to move said shield from said first position to said second position when pressure at said inlet drops below said predetermined magnitude.
 4. The apparatus recited in claim 3 in which said means to move said shield comprises a flexible diaphragm, spring means biasing said diaphragm in a direction to move said heat shield to said second position and means communicating one side of said diaphragm with said inlet pressure to oppose a bias of said spring means and retain said shield in said first position as a consequence of said inlet pressure.
 5. The apparatus recited in Claim 2 wherein said means responsive to line pressure comprises a fluid conduit to direct line fluid against said fuse, and valve means to prevent passage of fluid through said conduit when pressure at said inlet is above said predetermined magnitude, said valve means being movable when pressure at said inlet falls below said predetermined magnitude to pass line fluid through said conduit and against said fuse.
 6. The apparatus recited in claim 5 in which said conduit is formed of malleable material to enable adjustable positioning of the outlet end thereof.
 7. The apparatus recited in claim 5 wherein said inlet defining means includes a tubular adaptor, said conduit and said valve means being mounted on said adaptor.
 8. Apparatus for controlling the release temperature of a thermal fuse on a sprinkler head for fixed fire extinguishing systems of the type in which a fluid extinguishant under pressure is supplied by pipes to a plurality of such heads, said device comprising: actuating means movable from a first position to a second position in response to line pressure at the sprinkler head falling below a predetermined magnitude and means operably associated with said actuating means for inhibiting the effect of ambient temperature on said fuse upon movement of said actuating means to said second position.
 9. The apparatus recited in claim 8 wherein said last mentioned means includes a heat shield movable to a position to shield said fuse from increases in ambient temperature upon movement of said actuating means to said second position.
 10. The apparatus recited in claim 8 wherein said last mentioned means comprises a bleed conduit for directing extinguishant against said fuse, and wherein said actuating means comprises a pressure responsive valve which opens said bleed conduit upon movement of said valve from said first position to said second position.
 11. The apparatus recited in claim 10 including a tubular adaptor for connection between the sprinkler head and the pipes of the fire extinguishing system, said bleed conduit and said valve being mounted in said adaptor, and said bleed conduit being deformable to adjust the discharge end thereof with respect to the fuse.
 12. A fire protection system comprising at least one extinguishant discharge head mounted in an elevated position in the space to be protected, means for supplying an extinguishant under line pressure to said head, releasable means normally preventing the discharge of extinguishant from said head, fire sensing means operable upon the existence of a fire to release said releasable means, and means responsive to a predetermined condition of said system to inhibit operation of said sensing means.
 13. The system recited in claim 12 wherein said fire sensing means comprises a thermal fuse to release said releasable means at predetermined ambient temperatures.
 14. The system recited in claim 13 in which said means to inhibit operation of said sensing means comprises a heat shield movable between a first position in which said fuse is exposed fully to ambient temperatures, and a second position in which said fuse is shielded thereby from increases in ambient temperature, and means to move said shield from said first position to said second position in response to said predetermined condition of said system.
 15. The system recited in claim 14 in which said means to move said shield comprises a flexible diaphragm, spring means biasing said diaphragm in a direction to move said heat shield to said second position, and means communicating one side of said diaphragm with said extinguishant to oppose the bias of said spring means and retain said shield in said first position as a consequence of said inlet pressure.
 16. The system recited in claim 13 wherein said predetermined condition of said system is a predetermined extinguishant pressure at said head and wherein said means to inhibit operation of said sensing means comprises a fluid conduit to direct line fluid against said fuse, anD valve means to prevent passage of fluid through said conduit when the extinguishant pressure at said head is above said predetermined magnitude, said valve means being movable when said pressure falls below said predetermined magnitude to pass line fluid through said conduit and against said fuse.
 17. The system recited in claim 16 in which said conduit is formed of malleable material to enable adjustable positioning of the outlet end thereof.
 18. The system of claim 12 wherein said predetermined condition of said system is the extinguishant pressure at each of said heads. 